Treating glass fibers



czar/ Patented Mar. 30, 1943 TREATING GLASS FIBERS James Franklin Hyde, Corning, N. Y., assig-nor to Owens-Corning Fiberglas Corporation, a corporation of Delaware No Drawing. Application April 15, 1940, Serial No. 329,827

Claims.

This invention relates to glass flbers and treatments thereof and is a continuation in part, of my pending application Serial Number 154,101, filed July 16,1937, which was issued June 17, 1941, as Patent No. 2,245,783.

The object of the invention is to increase the electrical resistance and mechanical strength of glass fibers when they are subjected to humid conditions or are wet with water.

Glass fibers in general have a high electrical resistance and good flex strength when dry and fabrics made therefrom are particularly suitable for insulation coverings for cables and other electrical conductors. These properties depreciate more or less when the fibers are moist or wet with water. Such deterioration is particularly serious in the case of insulation which must be subject to wet or humid conditions such as the coverings for marine cables, etc. Flex strength is measured by drawing the fibrous yarn or tabric around a steel mandrel, one-eighth inch in diameter and free to rotate, the flbers being tensed by a weight of three-fourths of a pound. When dry, a glass fiber yarn will withstand this test for about 700 tolOOO flexes without breaking, but when wet, breakage occurs after only 30 to 40 flexes.

I hav discovered that the electrical resistance and flex strength of glass fibers under wet or humid conditions is increased many fold by treating them with an aqueous solution of a metallic salt, preferably a chloride, fluoride, nitrate, acetate or sulfate salt.

I have further found that this efiect is, parcularly marked in glasses which are substantially free from alkali metal oxides.

Other features of the invention will become apparent as the description proceeds.

In practicing the invention the fibers or textiles made therefrom are immersed in an aqueous solution of the desired salt which may be either cold or heated. If desired, an autoclave may be employed, but in this case some salts chemically attack the glass and should be avoided. A concentration of about 59* by weight is preferred. but concentrations up to 40% or mor may be used for salts which are sufliciently soluble and which do not attack th glass under these conditions. In general an immersion time of one to eight hours is sufficient although longer times may be employed. After the treatment the material is washed thoroughly to remove the residual salt from its surface after which it is dr'ed.

The following table shows the improvement in electrical surface resistance of glass insulating tape as measured in megohms per inch in high relative humidities' for stated times after the above described treatment with various salt solutions. Glass A is an ordinary soda lime glass containing about 18% oi. alkali oxide and glass B is a. magnesia lime glass containing about 17% of alumina and not more than 2% of alkali oxide.

Conditions or test Cilas Sn. solution Megohx RH Time Percent Days Per inch A Untreated... i 5

A 5%lcad n trate and lead oxide.. 85 l 800 A 5% a pnc nitrate and 1% 85 1 H10 cupnc carbonate.

A 20% lead acetate and 20'}; cop- 85 l 15, (I!) per acetate.

A (Head acetate-..... as l Infinite A 15% aluminum acetate and 55 l 115 2"; aluminum oxide.

A l07 silver nitrate R5 1 3'0 A 10% titanous chloride. 78 1 A Said. titanic chloride 78 1 I3 A 5% barium nitrate and 1% 7S l 230 barium carbonate.

B Untreated 85 l 50 B do. H8 7 150 B zincchloride.... 85 1 50,111)

D 5 '75 lead nitrate and lead oxide it) 1 50, 0G)

B 5% cupric nitrate and 1% 65 1 18, (D0

cupric carbonate.

1i 5% ammonium fluoride R' 1 50,000

E 20% lead acetate and 20'? 8a infinite cupric acetate.

B 15% aluminum acetate and 2']; 83 1 i0, 000

aluminum oxide.

B in; silver nitrate 85 l 50, (ID

I?" 109; titanous chloride 78 l 2, 000

ll Satd. titanic chloride. 78 1 3.000

B 57 barium nitrate and .lf' 78 l Infinite barium carbonate.

B lead acetate... 85 l Infinite B 15'; lithium acetate. 2 Infinite )3 15? barium acetate.. 15 22 100.000

B 15% magnesium acetaie.. 95 22 12,000

E l 'f} ammonium acetate *5 22 l, 000

B 15%];ad acetate and 8% load 5 2 Infinite on o.

B 1.5% cadmium acetate and 95 Infinite cadmium hydroxide.

B 15'7r copper sulfate (ornmom- 98 l 700 meal). I

From the above table it will be noted that in general a treatment with any particular salt solution is more effective on the low alkali glass B than it is on the soda lime glass A. Moreover, solutions containing a lead salt are more effective with both glasses than solutions of other salts and lead acetate is particularly efiective.

The following table shows the increase in flex strength of yarns composed of continuous fibers of a glass substantially free from alkali and containing about 23% of oxides of the second periodic group together with A: and 13203 when treated with 5% aqueous salt solutions and tested wet by the above described method.

Here again it will be noted that the lead salts are particularly eii'ective and that the value ior lead acetate exceeds all others.

What is claimed is:

l. The method of increasing the wet fiex strength and electrical surface resistance under humid conditions of glass fibers which includes immersing the fibers for one to eight hours in an aqueous solution containing a metallic salt of an acid selected from the group consisting of acetic, hydrochloric. hydrofluoric, nitric and suliuric acids and thereafter washing the fibers with water.

2. Method according to claim -1 in which the metallic salt is a lead salt.

3. Method according to claim 1 in which the glass contains less than 2% 0! alkali metal oxide.

4. The method of increasing the wet fiex strength and electrical surface resistance under humid conditions of glass fibers which includes immersing the fibers from one to eight hours in an aqueous solution containing from 5% to 40% by weight of lead acetate, and thereafter washin: the fibers with water.

5. The method or increasing the wet fiex strength and electrical surface resistance under humid conditions of glam fibers which includes immersing the fibers from one to eight hours in an aqueous solution of a metallic acetate. and thereafter washing the fibers with water.

JAMES FRANKLIN HYDE. 

